The 507 carat stone, which could be worth in excess of $20m (£12.5m), was found with three other large diamonds.

They were discovered at the famous Cullinan mine, where the largest diamond in history was found more than 100 years ago, reports BBC News.

Johan Dippenaar, the company's chief executive said in a statement Tuesday that the 507.55-carat gem was of "exceptional color and clarity."

No value has been give yet for the diamond, which weighs just over 100 grams.

The mine also produced the largest diamond ever found, the Cullinan, at 3,106 carats in the rough. That finished stone is set in Britain's Imperial Scepter as part of the Crown Jewels, The Associated Press reports.

The world’s biggest certified diamond is the 3,106-carat Cullinan, found at the mine near Pretoria, South Africa in 1905. It was cut to form the Great Star of Africa and the Lesser Star of Africa, set in the Crown Jewels of Britain.

Petra sold a 7.03-carat blue diamond, cut from a 26.58-carat rough stone found at the mine, for $9.48 million in May, Bloomberg informs.

Not that long ago, American soldiers would train their skills to counter insurgent and partisan military organizations. These days, they are trained to show resistance to the regular army of a potential adversary